The present invention relates to a magnetic reproducing apparatus for reproducing by use of a ring type magnetic head a digital signal recorded on a perpendicular magnetic recording medium.
The perpendicular magnetic recording method is a method for recording information by magnetizing a recording medium in a direction of thickness thereof and is expected to be applied to a high density digital recording storage.
With a ring type magnetic head (to be simply referred to as a ring head herebelow) used as a magnetic recording and reproducing head in the perpendicular magnetic recording method, a waveform of FIG. 2B is obtained when information at an isolated magnetization transition is reproduced, where the waveform has asymmetric positive and negative peaks (to be referred to as isolated waveshape herebelow). As a method for discriminating a position of magnetization transition from such a waveform, a method for processing a waveform of a reproduced signal has already been proposed by the inventors of the present invention and the coinventors (Japanese Patent Application Laid Open No. 60-150,316). That is, as shown in FIG. 2A, a reproduced signal 1 outputted from a ring head is delayed by a delay line 5, the resultant delayed signal 2 and a signal 3 obtained by adjusting the amplitude of the reproduced signal 1 by use of an attenuator 6 are amplified by a differential amplifier 23 so that these signals are overlapped with a time difference therebetween, the difference being equal to a time interval between the positive and negative peaks of the isolated waveshape, thereby producing a signal 4 in which the asymmetry has been removed. A zero-cross point of the signal 4 is detected as a magnetization transition.
In a digital recording storage, to effect a highly accurate information reproduction, a timing jitter must be essentially minimized in the pulse reproduced at magnetization transition; however, this has not been fully considered in the prior art technique.